In electronic components, such as coils and noise filters, in which a winding is provided around a core composed of a magnetic material, e.g., ferrite, the winding is often coated with a resin containing a powdery magnetic material composed of ferrite or the like in order to improve characteristics of the electronic components. For example, in a coil in which a winding is coated with a resin containing a magnetic material, a quasi-closed magnetic circuit is formed, thus increasing the inductance. Furthermore, the coating reinforces the strength of the core. Note that in some cases, instead of providing a winding, a spiral conductive pattern may be disposed on the outer peripheral surface of the core.
Furthermore, in some cases, a resin incorporated with magnetic material powder may be used as the core.
For example, Japanese Unexamined Patent Application Publication No. 2003-297642 (Patent Document 1) discloses a chip inductor which includes a core, a coil wound around the core, an external coating material integrally provided so as to cover the outer periphery of the core and the coil, and terminal electrodes. In the chip inductor of Patent Document 1, the core and the external coating material are each composed of a material prepared by incorporating functional material powder of a magnetic material having an average particle size of 1 to 10 μm into a resin. It is disclosed that it is possible to use, as the magnetic material, MnZn ferrite, NiZn ferrite, MnMgZn ferrite, NiCuZn ferrite (NiZnCu ferrite), Ba ferrite, Fe2O3, Fe3O4 (magnetite), or the like.